The present invention relates generally to transducer moving or feeding mechanisms in apparatuses for recording and reproducing of signals on and from rotary recording mediums. More particularly the invention relates to a mechanism for feeding in traverse movement a transducer for carrying out recording and reproducing signals on and from a rotary recording medium, the mechanism being capable of thus feeding the transducer in an accurate and positive driving power transmission state and, moreover, without shock or vibration.
Heretofore, apparatuses for recording and reproducing magnetic discs of the type wherein a magnetic head is caused to move intermittently over a rotary magnetic disc thereby to record and reproduce video signals with concentric tracks have been reduced to practice. As a device for moving the head in an apparatus of this type for recording and reproducing magnetic discs, the same assignee as that of the present invention, has proposed a device as disclosed in the specification of U.S. Pat. No. 3,749,827, entitled "ENDLESS NON-METALLIC FOR INTERMITTENTLY MOVING A TRANSDUCER HEAD TRANSVERSELY ACROSS A ROTARY MAGNETIC HEAD", in which an endless belt passed around a driving shaft driven by a stepping motor (pulse motor) and a driven shaft are moved intermittently, and a magnetic head mounted on the endless belt is caused to move in traverse movement over the magnetic disc.
This device, however, has been accompanied by difficulties such as permanent elongation in the endless belt as result of a long period of use and the occurrence of uneven elongation in the belt when the driving shaft and the driven shaft are not precisely parallel, whereby the magnetic head cannot be moved over the magnetic disc accurately and positively over specific tracks. A further problem accompanying this device is that the magnetic head cannot be moved with accurate pitch because of occurrences such as slippage between the belt and the shafts, variation in the difference between the tensions in the belt on the driving shaft side and on the driven shaft side, and stretching and shrinking of the belt due to variations in temperature.
Accordingly, in order to solve the above described problems, we have devised a moving mechanism so constituted that, instead of the head moving mechanism described above wherein a head and shafts are used, a rack is fixed to a moving base or carriage on which a magnetic head is fixedly mounted, and a pinion provided on the rotor shaft of a motor is adapted to mesh with this rack, whereby rotation of the pinion by the motor causes the rack, and therefore the head, to move. In a device of this mechanical arrangement, however, there are a number of problems such as low accuracy of movement position of the head due to backlash between the rack and the pinion and transmission to the head of shocks between the rack and the rotating pinion, whereby satisfactory head movement cannot be attained. These problems become particularly serious in the case of an apparatus for recording and reproducing magnetic discs of a system wherein the motor rotates intermittently, and the head is moved intermittently.